The visual world is largely processed in parallel visual system circuitry, and the fundamental units of parallel processing are discrete cell types. Distinct cell types representing different aspects of the visual scene are first found in the retina, yet what these types are or where they project in the brain is only partially understood. A critical limitation has been that distinguishing cell types requires recording the physiology and anatomy of many cells at once. We propose to develop for the first time a technique to simultaneously record the physiology of hundreds of primate retinal ganglion cells (RGCs) in conjunction with anatomical visualization of recorded cells. This technique will establish the morphological cell types of RGCs identified physiologically, including a new class recently observed in our recordings, thereby establishing those cells' brain projections and revealing which visual processing tasks they participate in. It is not coincidental or arbitrary that different physiological cell classes have unique morphologies; surely their structure serves their function. By comparing the anatomy and physiology of many cells at once, we will determine how the dendritic branching patterns of RGCs shape their spatial light sensitivity. [unreadable] [unreadable]